An exposure apparatus used to manufacture a device such as a semiconductor device comprises an exposure unit, alignment measurement unit, substrate stage, and the like. The exposure unit includes an exposure light source, illumination system and projection optical system. An exposure beam containing pattern information is generated by an exposure light from the light source illuminating an original plate having a pattern. The projection system projects the exposure beam containing the pattern information of the original plate onto a substrate. The alignment measurement unit measures the position of an alignment mark formed on the substrate before exposure. The substrate stage moves the substrate before exposure to an alignment measurement position immediately under the alignment measurement unit, and the substrate after alignment to an exposure position immediately under the exposure unit.
Conventionally, the illuminance of the light source of the exposure unit has been increased to improve the throughput of the exposure apparatus. The performances of the respective units have been improved such as pursuing an alignment measurement unit that performs a measurement process within a shorter period of time or a substrate stage that moves at higher speed. Furthermore, an exposure apparatus has been put into practical use in which two substrate stages are provided and, while one substrate stage is used as an exposure stage, the other substrate stage is used as an alignment measurement stage, to perform exposure operation and alignment operation in a parallel manner.
In order to form a small latent image pattern on a substrate, as an exposure beam, a short-wavelength exposure beam has been introduced into practical use, e.g., a charged particle beam such as an electron beam, an F2 laser beam, or an EUV beam. To use such an exposure beam, the optical path of the exposure beam from the exposure light source to the substrate must be arranged in a space held at a predetermined vacuum degree or a nitrogen space with a predetermined concentration depending on the type of exposure light source. For this purpose, various types of units in the exposure apparatus, e.g., the exposure unit, alignment measurement unit, substrate stage, and the like are arranged in a chamber, and the interior of the chamber is maintained at a reduced-pressure environment or nitrogen atmosphere.
When the exposure apparatus is configured to comprise a single substrate stage, it cannot perform the exposure operation and alignment measurement apparatus simultaneously. When the exposure apparatus comprises two stages, it can perform the exposure operation and alignment measurement operation simultaneously, but the size of its stage arrangement becomes inevitably large. To cope with the trend a larger wafer size, both the exposure apparatus comprising the single stage and the exposure apparatus comprising the two stages tend to have larger sizes.
When the stage arrangement size becomes large in this manner, if the exposure apparatus uses a short-wavelength exposure beam, e.g., a charged particle beam such as an electron beam, an F2 laser beam, or an EUV beam, the size of the chamber which accommodates the units such as the exposure unit, alignment measurement unit, and substrate stage and isolates its inner environment from the outer environment (atmosphere) becomes large. An increase in chamber size leads to a bulky vacuum device or purge device which maintains the inner space of the chamber at a predetermined vacuum degree or atmosphere.
In addition, an increase in chamber size increases the time required to change the inner space of the chamber from the atmospheric environment to a predetermined reduced-pressure environment or atmosphere when the exposure apparatus is started.
To suppress the capacity of the chamber, it is effective to arrange the alignment measurement unit outside the exposure chamber and perform alignment measurement in the atmosphere, as proposed in this application. With this scheme, to transport a substrate after alignment measurement into the exposure chamber, typically, a load-lock chamber which substitutes the outer atmosphere in the substrate transport path by the atmosphere in the exposure chamber is arranged adjacent to the exposure chamber.
In this case, note that when the load-lock chamber in an atmospheric state is to be exhausted to a predetermined vacuum degree, the substrate is deprived of heat due to adiabatic expansion, so the substrate temperature decreases and the substrate shrinks. If the substrate size changes, a value obtained by alignment measurement in the atmosphere may include an error in the exposure chamber. Even when the load-lock chamber is purged with a gas such as nitrogen, if the atmospheric temperature and the gas temperature differ, the substrate size changes in accordance with the temperature difference between them.